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BJO Online First, published on February 10, 2014 as 10.1136/bjophthalmol-2013-304228 Global issues
Prevalence of refractive errors in the European adult population: the Gutenberg Health Study (GHS) Christian Wolfram,1 René Höhn,1 Ulrike Kottler,1 Philipp Wild,2 Maria Blettner,3 Jens Bühren,4 Norbert Pfeiffer,1 Alireza Mirshahi1 1
Department of Ophthalmology, University Medical Center Mainz, Mainz, Germany 2 Department of Internal Medicine, University Medical Center Mainz, Mainz, Germany 3 University Medical Center Mainz, Institute of Medical Biostatistics, Epidemiology and Informatics (IMBEI), Mainz, Germany 4 Department of Ophthalmology, University Hospital Frankfurt, Frankfurt, Germany Correspondence to Dr Christian Wolfram, University Medical Center, Department of Ophthalmology Mainz, Langenbeckstr. 1, Mainz D-55131, Germany; [email protected] Received 30 August 2013 Revised 16 December 2013 Accepted 10 January 2014
ABSTRACT Objective To study the distribution of refractive errors among adults of European descent. Design Population-based eye study in Germany with15 010 participants aged 35–74 years. Methods The study participants underwent a detailed ophthalmic examination according to a standardised protocol. Refractive error was determined by an automatic refraction device (Humphrey HARK 599) without cycloplegia. Definitions for the analysis were myopia +0.5 D, astigmatism >0.5 cylinder D and anisometropia >1.0 D difference in the spherical equivalent between the eyes. Exclusion criterion was previous cataract or refractive surgery. Results 13 959 subjects were eligible. Refractive errors ranged from −21.5 to +13.88 D. Myopia was present in 35.1% of this study sample, hyperopia in 31.8%, astigmatism in 32.3% and anisometropia in 13.5%. The prevalence of myopia decreased, while the prevalence of hyperopia, astigmatism and anisometropia increased with age. 3.5% of the study sample had no refractive correction for their ametropia. Conclusions Refractive errors affect the majority of the population. The Gutenberg Health Study sample contains more myopes than other study cohorts in adult populations. Our findings do not support the hypothesis of a generally lower prevalence of myopia among adults in Europe as compared with East Asia.
INTRODUCTION
To cite: Wolfram C, Höhn R, Kottler U, et al. Br J Ophthalmol Published Online First: [ please include Day Month Year] doi:10.1136/bjophthalmol2013-304228
Refractive errors are very common and affect the majority of the population. Due to the fact that most refractive errors can be corrected easily and usually have no direct pathological implications, the epidemiology of refractive errors has not been studied in depth, particularly not for the European population. Population-based surveys in other regions of the world demonstrated that the prevalence of myopia tends to decrease with age, whereas the prevalence of hyperopia reveals the opposite tendency.1–6 Reports of possible gender differences in the prevalence of refractive errors have been controversial. Women have been found to be more hyperopic1 or more myopic.7 Other studies failed to confirm any gender differences.4 8 9 Prevalence rates of refractive errors have also been reported to differ by race, with Caucasians presenting higher prevalence rates for myopia and hyperopia than black or Hispanic subjects.3 A higher prevalence of myopia among Asians has been discussed,10 but recent epidemiological studies do not support this hypothesis.4 7
Wolfram C, et al. BrArticle J Ophthalmol 2014;0:1–5. Copyright author (or doi:10.1136/bjophthalmol-2013-304228 their employer) 2014. Produced
Both genetic and environmental factors have been found to play a role in the aetiology of refractive errors.11 Although there is evidence that refractive errors among siblings correlate closely,12 the genetic background of myopia remains unclear, as it may involve a complex interaction of multiple genes.13 Environmental associations have also been described between myopia and urban environment as well as with higher education.6 Possible ethnic, genetic and environmental differences make it difficult to project findings from other areas in the world and to apply them to the situation in Europe. This study is the first population-based cross-sectional study in Germany to assess the prevalence and distribution of refractive errors in the general adult population in Germany.
METHODS The Gutenberg Health Study (GHS) is a population-based, prospective, observational cohort study in the Rhine-Main region, located in the State of Rhineland-Palatine in midwestern Germany. It has a total of 15 010 participants aged 35–74 years who were evaluated after random sampling from the regional registration office. Aside from the investigation of ophthalmological conditions and eye diseases, the study also focuses on cardiovascular and metabolic diseases, cancer, diseases of the immune system and mental diseases. A detailed description of the GHS and the study methods have been published by Wild et al.14 Inclusion criteria were sufficient knowledge of the German language to understand the study documents, and the physical and psychological capabilities to travel to the study centre and cooperate during the investigations. Exclusion criteria for the analysis of refractive errors were previous cataract or refractive surgery or other reasons that may have distorted the refraction of the eye (such as a history of perforating corneal injury). Cases with information on only one eye were excluded as well in order to allow comparability of the refraction between both eyes. The participants’ examinations took place at the study centre at the University Medical Center in Mainz between April 2007 and April 2012. Written informed consent was obtained from each participant prior to any examination, according to the tenets of the Declaration of Helsinki. All participants underwent extensive medical examinations as well as a comprehensive ophthalmological examination. The refraction was determined automatically by an automatic refractor (Humphrey HARK 599). Cycloplegic medication
by BMJ Publishing Group Ltd under licence.
1
Downloaded from bjo.bmj.com on May 16, 2014 - Published by group.bmj.com
Global issues was not used. Refractive errors were measured in spherical and cylindrical dioptres (D), where for cylindrical power a negative sign convention was used. Our definitions for refractive errors were myopia +0.5 spherical D, anisometropia >1.0 spherical D difference between eyes and astigmatism >0.5 cylinder D, as these are the most commonly used definitions for refractive errors in the literature. We then calculated the prevalence rates of different definitions of myopia (+3.0 D). Participants were also asked about their use of glasses or contact lenses. The prevalence of uncorrected refractive errors was then assessed by the presence of myopia or hyperopia (according to the autorefractive result) in both eyes and the information that no refractive correction was used. Prevalence rates of the respective refractive errors were assessed by computing absolute and relative frequency of refractive errors in the whole cohort and in subgroups after stratifying for age and gender. 95% CIs were calculated for all the relative frequencies of refractive errors in the population. Differences in frequencies of findings between men and women were assessed by logistic regression adjusting for age. Testing for age trends was performed by logistic regression adjusting for sex. Analyses were done using PASW Statistics V.20 and SAS V.9.2.
Figure 1 2
RESULTS Of the entire study sample, 692 subjects had undergone cataract surgery and 74 subjects had had refractive surgery and were excluded from the analysis. An additional 64 subjects were excluded due to a history of corneal injuries, corneal transplantation or other conditions that may have affected the refraction. Data on refractive errors were missing in 237 subjects, including those whose refractive data were available for one eye only. Data were missing mainly for technical reasons or unwillingness to participate in the ophthalmic examination; thus, data of 13 959 study participants were included in the analysis. The mean value of refractive errors in the study population was −0.401 D for right eyes and −0.395 D for left eyes. We observed no statistically significant difference between left and right eyes. For the purpose of easier illustration, the following findings therefore describe right eyes only. Figure 1 shows the distribution of refractive errors within the study population. The range of refractive errors was −21.50 to +13.88 spherical D. The graph does not follow a Gaussian distribution as it is skewed towards myopia (v=−1.457). The overall prevalences of refractive errors in the GHS are shown in table 1. The prevalence of myopia defined as 0.5 cyl D)
Anisometropia (>1 sph D difference)
N
%
N
%
N
%
N
%
4895 2534
35.1 (34.3–35.9) 35.9 (34.8–37.0)
4439 2173
31.8 (31.0–32.6) 30.8 (29.7–31.9)
4513 2429
32.3 (31.6–33.1) 34.4 (33.3–35.5)
1880 951
13.5 (12.9–14.0) 13.5 (12.7–14.3)
2361
34.2 (33.1–35.4)
2266
32.9 (31.8–34.0)
2084
30.2 (29.1–31.3)
929
13.5 (12.7–14.3)
0.922 (0.961–0.988) p=0.021 1474 46.5 1707 44.3 1090 29.3 624 19.5 0.963 (0.960–0.966) p
BJO Online First, published on February 10, 2014 as 10.1136/bjophthalmol-2013-304228 Global issues
Prevalence of refractive errors in the European adult population: the Gutenberg Health Study (GHS) Christian Wolfram,1 René Höhn,1 Ulrike Kottler,1 Philipp Wild,2 Maria Blettner,3 Jens Bühren,4 Norbert Pfeiffer,1 Alireza Mirshahi1 1
Department of Ophthalmology, University Medical Center Mainz, Mainz, Germany 2 Department of Internal Medicine, University Medical Center Mainz, Mainz, Germany 3 University Medical Center Mainz, Institute of Medical Biostatistics, Epidemiology and Informatics (IMBEI), Mainz, Germany 4 Department of Ophthalmology, University Hospital Frankfurt, Frankfurt, Germany Correspondence to Dr Christian Wolfram, University Medical Center, Department of Ophthalmology Mainz, Langenbeckstr. 1, Mainz D-55131, Germany; [email protected] Received 30 August 2013 Revised 16 December 2013 Accepted 10 January 2014
ABSTRACT Objective To study the distribution of refractive errors among adults of European descent. Design Population-based eye study in Germany with15 010 participants aged 35–74 years. Methods The study participants underwent a detailed ophthalmic examination according to a standardised protocol. Refractive error was determined by an automatic refraction device (Humphrey HARK 599) without cycloplegia. Definitions for the analysis were myopia +0.5 D, astigmatism >0.5 cylinder D and anisometropia >1.0 D difference in the spherical equivalent between the eyes. Exclusion criterion was previous cataract or refractive surgery. Results 13 959 subjects were eligible. Refractive errors ranged from −21.5 to +13.88 D. Myopia was present in 35.1% of this study sample, hyperopia in 31.8%, astigmatism in 32.3% and anisometropia in 13.5%. The prevalence of myopia decreased, while the prevalence of hyperopia, astigmatism and anisometropia increased with age. 3.5% of the study sample had no refractive correction for their ametropia. Conclusions Refractive errors affect the majority of the population. The Gutenberg Health Study sample contains more myopes than other study cohorts in adult populations. Our findings do not support the hypothesis of a generally lower prevalence of myopia among adults in Europe as compared with East Asia.
INTRODUCTION
To cite: Wolfram C, Höhn R, Kottler U, et al. Br J Ophthalmol Published Online First: [ please include Day Month Year] doi:10.1136/bjophthalmol2013-304228
Refractive errors are very common and affect the majority of the population. Due to the fact that most refractive errors can be corrected easily and usually have no direct pathological implications, the epidemiology of refractive errors has not been studied in depth, particularly not for the European population. Population-based surveys in other regions of the world demonstrated that the prevalence of myopia tends to decrease with age, whereas the prevalence of hyperopia reveals the opposite tendency.1–6 Reports of possible gender differences in the prevalence of refractive errors have been controversial. Women have been found to be more hyperopic1 or more myopic.7 Other studies failed to confirm any gender differences.4 8 9 Prevalence rates of refractive errors have also been reported to differ by race, with Caucasians presenting higher prevalence rates for myopia and hyperopia than black or Hispanic subjects.3 A higher prevalence of myopia among Asians has been discussed,10 but recent epidemiological studies do not support this hypothesis.4 7
Wolfram C, et al. BrArticle J Ophthalmol 2014;0:1–5. Copyright author (or doi:10.1136/bjophthalmol-2013-304228 their employer) 2014. Produced
Both genetic and environmental factors have been found to play a role in the aetiology of refractive errors.11 Although there is evidence that refractive errors among siblings correlate closely,12 the genetic background of myopia remains unclear, as it may involve a complex interaction of multiple genes.13 Environmental associations have also been described between myopia and urban environment as well as with higher education.6 Possible ethnic, genetic and environmental differences make it difficult to project findings from other areas in the world and to apply them to the situation in Europe. This study is the first population-based cross-sectional study in Germany to assess the prevalence and distribution of refractive errors in the general adult population in Germany.
METHODS The Gutenberg Health Study (GHS) is a population-based, prospective, observational cohort study in the Rhine-Main region, located in the State of Rhineland-Palatine in midwestern Germany. It has a total of 15 010 participants aged 35–74 years who were evaluated after random sampling from the regional registration office. Aside from the investigation of ophthalmological conditions and eye diseases, the study also focuses on cardiovascular and metabolic diseases, cancer, diseases of the immune system and mental diseases. A detailed description of the GHS and the study methods have been published by Wild et al.14 Inclusion criteria were sufficient knowledge of the German language to understand the study documents, and the physical and psychological capabilities to travel to the study centre and cooperate during the investigations. Exclusion criteria for the analysis of refractive errors were previous cataract or refractive surgery or other reasons that may have distorted the refraction of the eye (such as a history of perforating corneal injury). Cases with information on only one eye were excluded as well in order to allow comparability of the refraction between both eyes. The participants’ examinations took place at the study centre at the University Medical Center in Mainz between April 2007 and April 2012. Written informed consent was obtained from each participant prior to any examination, according to the tenets of the Declaration of Helsinki. All participants underwent extensive medical examinations as well as a comprehensive ophthalmological examination. The refraction was determined automatically by an automatic refractor (Humphrey HARK 599). Cycloplegic medication
by BMJ Publishing Group Ltd under licence.
1
Downloaded from bjo.bmj.com on May 16, 2014 - Published by group.bmj.com
Global issues was not used. Refractive errors were measured in spherical and cylindrical dioptres (D), where for cylindrical power a negative sign convention was used. Our definitions for refractive errors were myopia +0.5 spherical D, anisometropia >1.0 spherical D difference between eyes and astigmatism >0.5 cylinder D, as these are the most commonly used definitions for refractive errors in the literature. We then calculated the prevalence rates of different definitions of myopia (+3.0 D). Participants were also asked about their use of glasses or contact lenses. The prevalence of uncorrected refractive errors was then assessed by the presence of myopia or hyperopia (according to the autorefractive result) in both eyes and the information that no refractive correction was used. Prevalence rates of the respective refractive errors were assessed by computing absolute and relative frequency of refractive errors in the whole cohort and in subgroups after stratifying for age and gender. 95% CIs were calculated for all the relative frequencies of refractive errors in the population. Differences in frequencies of findings between men and women were assessed by logistic regression adjusting for age. Testing for age trends was performed by logistic regression adjusting for sex. Analyses were done using PASW Statistics V.20 and SAS V.9.2.
Figure 1 2
RESULTS Of the entire study sample, 692 subjects had undergone cataract surgery and 74 subjects had had refractive surgery and were excluded from the analysis. An additional 64 subjects were excluded due to a history of corneal injuries, corneal transplantation or other conditions that may have affected the refraction. Data on refractive errors were missing in 237 subjects, including those whose refractive data were available for one eye only. Data were missing mainly for technical reasons or unwillingness to participate in the ophthalmic examination; thus, data of 13 959 study participants were included in the analysis. The mean value of refractive errors in the study population was −0.401 D for right eyes and −0.395 D for left eyes. We observed no statistically significant difference between left and right eyes. For the purpose of easier illustration, the following findings therefore describe right eyes only. Figure 1 shows the distribution of refractive errors within the study population. The range of refractive errors was −21.50 to +13.88 spherical D. The graph does not follow a Gaussian distribution as it is skewed towards myopia (v=−1.457). The overall prevalences of refractive errors in the GHS are shown in table 1. The prevalence of myopia defined as 0.5 cyl D)
Anisometropia (>1 sph D difference)
N
%
N
%
N
%
N
%
4895 2534
35.1 (34.3–35.9) 35.9 (34.8–37.0)
4439 2173
31.8 (31.0–32.6) 30.8 (29.7–31.9)
4513 2429
32.3 (31.6–33.1) 34.4 (33.3–35.5)
1880 951
13.5 (12.9–14.0) 13.5 (12.7–14.3)
2361
34.2 (33.1–35.4)
2266
32.9 (31.8–34.0)
2084
30.2 (29.1–31.3)
929
13.5 (12.7–14.3)
0.922 (0.961–0.988) p=0.021 1474 46.5 1707 44.3 1090 29.3 624 19.5 0.963 (0.960–0.966) p
